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Lifting a roundwood framed roof to replace top structural logs  RSS feed

 
Rob Irish
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Hi guys,

We have a log house from the 1930's. The top logs have got a rot situation going on I guess due to the leaky roof. We need to swap these with new logs before we can continue restoring this home.

The framing of the roof is in good condition, so we're going to keep that, but we're going to get rid of the old cracking asbestos shingles.

Anyways, what I've been trying to wrap my head around is, the question I'm asking is: how do we lift the roof enough so that we can get in new logs up top? I'm talking about the logs the roof frame attaches to.

I've made a scale 3d model of our house, minus the windows and everything else, just so you can see the house logs, beams and roof framing. Basically all the top logs the roof is sitting on are in urgent need of swapping.

So far the best I've thought of is to attach temporary lumber to the framing and then lift it with a series of tall jacks. Perhaps like these site built jacks (http://www.finehomebuilding.com/how-to/tips/site-built-roof-jacks.aspx). Then lift in the new logs already notched and ready to go well in advance and plug it all together. Jacks seem like they would work better at lifting a corner or a small area but coordinating many of them to lift a whole side of a roof seems a bit hairy.

Is there a special kind of jack for this? Is it unrealistic to do this sort of thing by yourself and a few other guys or is there typically professionals that can just rig up something and lift the roof and come back and get their gear once you've finished? ie rental setup?

Any ideas on how to approach this would be really awesome.

Thanks,
Rob
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from the side. The orange beams are not there now but act as a brace to connect the roof to jacks.
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roof elevated
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side view
 
Terry Ruth
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I personally would not try what you are proposing. It may appear to be the least expensive(new top plates, tooling) alternative but if you do more damage to that old roof structure/walls you will regret it. I'd shift the load bearing wall out to another wall on piers or a footing that now supports the rafters with more overhang you create with a double 2x fascia and box structure, then dig out, treat, and cover the rot in the top plates. Seal up the roof so it does not leak. You may want to consult a structural engineer. You'll have to if there is building and safety codes.

If you want to try what you are proposing I would not try and lift the entire roof, I'd lift one rafter at a time just enough to create a clearance gap, remove and replace sections toward the inside, outside if you can, and only what was absolutely necessary, treat the rest with an anti-fungi. If a skid steer reach up there use it just be careful. Shore each rafter until the new sill is in perhaps 2-3 at a time. I'd toe-in/drive some dowl pins down to lower two logs for lateral support if you can and/or bond it in somehow.

What 3d software are you using that has logs? Does it have square or rectangular ones too?
 
Rob Irish
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Ok thank you for that Terry.

Just thinking about the suggestion you said about lifting one rafter at a time and removing sections might actually be the way to go.

So basically build a little something to hold the weight of the rafter, cut out that section or treat it, and then just replace a bit of the log? The sections I'm concerned about are not just a little bit rotted, I mean they are like 80% gone.. You can just dig a few places out completely with a screwdriver.

There is one section of log that is 6 meters (20') that is too bad to repair and several rafters are connected to that. Would you split this log into pieces and put them up individually for each rafter? I would imagine as long as each log section are pegged into the log below it should be structurally ok. Is that how it is typically done?

There are a few tractors in the area we might be able to use as well to help lift it a bit.

Some people have recommended just taking the whole roof apart and then reassembling later on. This way we can investigate each joint for rot. Seems a bit excessive though. Whatever the case, we're going to take the ceiling off this year which prevents us from really looking into the top logs all the way around the house and get a good idea from that I think. I don't think we'd like to take off the whole roof. So many nails and and dowl pins to undo and redo doesn't sound like my cup of tea.

The software I use is Cinema 4D. I use that because I freelance doing design and video work so it is totally overkill for this sort of thing and I built all the squared "logs" and roundwoods myself. Would be a lot easier if there were existing logs already. Actually though in Cinema 4D it is entirely possible to write a plugin that would make the creation of logs pretty quick. It does have a lot of architectural plugins. There are probably much cheaper alternatives, like Google's sketchup which is, I think free and renowned for its simplicity but I haven't used it.
 
Terry Ruth
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Right, you put your butt splices under a rafter that holds them down and together, and if you find the wall logs below the sill are damaged you do the same thing. You could put a log or big board on the bucket of a skid loader and get to two rafters at a time, perhaps three, just stop if you hearing cracking or see nails coming undone. The longer you can span boards the better just end under a rafter. Notch so the rafter sits on the sill and pin in each side of the splice and one between rafters. If you want to get conservative and make it really strong use some Simpson strong tie steel galvanized spice plates. Fungi treat. It's worth a try, if not redo the entire roof, damaged sills and walls.

If you pull the ceiling and do not find that the rafters clear span wall-to-wall and extend to create the eve soffits you may want to reconsider. Some soffits are put together with 2x extensions tied to rafters or outriggers like we are completing today. If that is the case, you may need to put in some large (.5 diameter bolts) at the splice to the rafters to take out the cantilever bending moment from the lift and be even more careful.

That is a very strong adhesive backed water and ice shield that does a great job at sealing the roof, nails, most are petro based is the problem. A metal standing seam roof goes over this we start today. The sheathing joints are taped with a ZIP very strong tape. Not that I agree with the design, it's the clients architects but it should hold the normal 25 years at least.

A clay stucco over the top of your wall might not be a bad idea to act as a water barrier and vapor (relative humidity) regulator: You wall probably either has a fungi food somewhere, or is not breathing and drying fast enough to prevent rot. I think this is being discussed here: http://www.permies.com/forums/f-75/wofati-earth-berm and here my thread: http://www.permies.com/t/43637/natural-building/Breathable-Walls

If you don't mind stucco over wood the entire wall. Wood across the grain depending on wind driven rain and relative humidity is not very hygroscopic. Along the grain it is. Clay is muliti-directional. Lineseed oil closes pores acts as a barrier but traps moisture in the wall, these timbers all have it indoors only, boiled. You want to control indoor humidity below 70% at all times. Depending on species wood across the grains does do that well again at regulating this indoor humidity, clay and lime do better, clay has been proven to regulate +/- 50% indoors and inside the wall by storage, wood just does not have this ability and to adsorb and dry as fast. Clay is like a breathing machine, it just need protection from water erosion as in large overhangs and lower wall, good drainage.
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Rob Irish
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Hi Terry.

It's has taken me a while to respond to really wrap my head around what you have said.

I had assumed the rafters are extending past the wall to create the eave soffit but after looking again, the rafters end at the wall. As you can see in the attached. This definitely throws my initial ideas out the window then for just jacking the whole thing up.

I don't mind stucco at all. One room we partially renovated to make it comfortable to live in the house and we clay plastered the interior. We'll be moving towards a combination of clay plasters and where the log work is nice keeping that visible inside.

You are right I think about the lack of breathing creating the rot. The first thing we did when we moved here was take off the unbreathable layers that somebody had added maybe 30 years ago. They covered the log walls with chipboard. And also they lined the sauna with aluminium foil. The areas that got the most attention in the last renovation all that time ago are the worse off. ironic.

By the look of it, how they've extended the soffit, if you can see from the pictures is it isn't close enough to the rafters to just put bolts through to make it solid.

I guess I could put up my own rafter extension easy enough, but is this all the best approach to replacing top logs? Was this the plan when people made log houses that if the top logs rotted they would have to take apart the roof and rebuild it? Or would they perhaps build some new support structure from inside the roof to take the weight? I'll attach a 3rd image with a little sketch to show what I mean.

You'll see I've got 2 jacks positioned on those horizontal beams (what are they called?) - if it could support I think this might be an easier option to lift this side of the roof a little bit enough to get out a section of log. Otherwise I put another jack on the rafter directly closer to the wall. Problem with it being so close to the wall is I imagine I'd need a bit more room to get the replacement log up. I don't know if this is common or not, but the horizontal beams I've got the scaffold sitting on goes in between the wall plate and the the log below, the mortise is split evenly between the 2.
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Rob Irish
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The sketch with the scaffold ad jacks on the inisde
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Bill Bradbury
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Hi Rob, I love your place! and man are you good at that 3d rendering!

First let's do some quick vocabulary;
Tie beam - the beam that goes between the walls to tie them together
halved - the type of joint used here between the tie beam and the top plate
top plate - the log at the top of the wall, where your rafters tie in
collar beam - ties a pair of rafters together
purlin - a longitudinal roof member that ties rafters together

I would remove the section of roofing above the rotted top plate, this will give you room to move and allow the affected rafters to move independently of the rest of the roof.

Then install a purlin beam across the affected rafters to tie them together and jack up on the purlin from jacks on the tie beams. I don't think you'll need to or want to jack on the collar beams as the joints are probably designed more to resist stretching.
When you jack this up, you need to be going in the direction of the ridge, not vertical, so you don't wrench the other joints and to get the tenon out. Then block it all, with posts to the tie beams. Do not rely on jacks to keep you safe!

Generally this would be a pinned tenon on the rafter going into the top plate's haunched mortise, but it looks like yours may just be wedged. You need to remove whatever type of pinning was used.

More photos please! Even if it's just informational.
 
Terry Ruth
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Hey Rob you're pretty good with that modeling it helps. Wow, interesting how they did the outriggers.

Are the sills resting on a chip board and is the rot attacking the sill up from the chip board? If you could post a pic of the rot it would be a good idea to understand the cause to come up with a corrective action. I see lots of sunlight so assuming you are seeing lots of moisture and wind driven rain in the addict?

Your cylinder jack looks like it should work depending on if the floor can take it. You could potentially still support several rafters with a board that spans across the center trusses as shown in the drawing.. The arrows through the tool shows how you want load to get distributed over the floor joist and floor you can accomplish any way you want. 2 floor joist minimum. Same with the rafter truss, to avoid point loads that can crack it span or distribute jacking loads over a larger area with a board(s) as shown. If the floor joist terminated to a rim joist on hangers lets me know. I got no idea how they did this back then or what they were thinking.

BTW, you don't want to load a TGI (I-beam) normal to the web ( usually osb) the way you have shown in the outer jack) I think you can get this done with just one jack used the right way. Worth a try.
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Bill Bradbury
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Rob Irish wrote:Ok thank you for that Terry.

Just thinking about the suggestion you said about lifting one rafter at a time and removing sections might actually be the way to go.

So basically build a little something to hold the weight of the rafter, cut out that section or treat it, and then just replace a bit of the log? The sections I'm concerned about are not just a little bit rotted, I mean they are like 80% gone.. You can just dig a few places out completely with a screwdriver.

There is one section of log that is 6 meters (20') that is too bad to repair and several rafters are connected to that. Would you split this log into pieces and put them up individually for each rafter? I would imagine as long as each log section are pegged into the log below it should be structurally ok. Is that how it is typically done?


The top plate needs to be a continuous log or be scarfed together. Scarf joints are time consuming to cut, so I would minimize the number of pieces used.Scarf Joint
 
Terry Ruth
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I like those scarf joints in a timber design. This is a log wall differs from post that are taking the load down to the ground from clear spanned beams. I'd agree those would be strong, but the splices with 12" log ties would be too when the rafter is on it, it resist both vertical and lateral loads. We are using those ties on much larger loads on a job I am on now. Wood pins carry the post and beam loads they bang in with linseed oil. Huge timbers are very capable of taking large loads if the joints are just as strong.

Without being there it has hard to tell what is fully going on. May be a good idea to get a structural engineer out there. At least you have some models and ideas to share. Who knows in the end it may be better and less time consuming to take that roof down and start over.
 
Rob Irish
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Hi Bill thanks a lot for those terms! I've been trying to figure out what they are called for a while. Will make it a lot easier now to talk about it, cheers!

3d modelling is almost second nature to me. I'm glad it helps.. especially when I haven't known the terms so I know it is hard to explain. There was a time when I thought I'd be an architect but by the time high school was a few years from over they had just about completely drained the desire to study out of me. And I'm a horrible drawer with a pen and pencil.

I'll attach a few more photos of up inside the roof if it helps..

You'll notice there is a rebar looking steel cable running parallel to the building. These are connected to the wall plates and obviously are there to work as the purpose of the tie beams. I think, it's hard to say without taking off the whole ceiling so I don't know yet, that they did some extension here once, as in made the building longer and wider, and rather than putting in log tie beams the whole width they just did this instead. I mean I'm sitting in one room now where I can see the tie beams, but then at the same height in the next room there are none. Would that make sense? It seems like a bit of a hack job.. and the house has had many owners who have applied their own hacks. My whole process so far has just been trying to understand the hacks and get rid of the garbage.

So we also want to get rid of those cables and restore it to log tie beams. We're thinking of going open ceiling because I want to look up and see nice wood work. Maybe a few sun roofs.

In one photo you can see new wood work that I've done. This was the first renovation I did where we took off the ceiling at the end of last summer. Then we realised how serious the rot was. With winter coming soon and this area taking up a quarter of the house I didn't feel I had much choice but to rebuild a roof to block out the cold. So I raised mini 8" x 8" tie beams with half joints either side that just span the space of those rooms and they are just sitting there loosely. You can see a few buckets of sawdust as well attempting to block out the holes I made in those wall plates seeing the extent of the rot.

I'll just repeat what you said in other words to make sure I understood right. Take off all the roof sheets in the area we're working on (I'm assuming you mean removing any that are touching any of the rafters that would need to be tilted). Make a purlin between those rafters. Jack up on the purlin towards the ridge. I'm wondering: what is going to happen to the joints on the other side of the tie beam that are rotating instead of being lifted? I guess I need to get a better look at those joints right? I will take some more photos of these top plate joints today
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Rob Irish
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Thanks a lot for that sketch! So this way only one jack would be needed to get an even lift. I see.

Terry Ruth wrote:
Are the sills resting on a chip board and is the rot attacking the sill up from the chip board? If you could post a pic of the rot it would be a good idea to understand the cause to come up with a corrective action. I see lots of sunlight so assuming you are seeing lots of moisture and wind driven rain in the addict?


Hi Terry, the chipboard was all on the interior. Mostly it seems the rot originates from the inside first. Likewise, the ceiling was wood planks, and when they renovated they just put up chipboard on that as well. All on the interior. Not a good situation. It's amazing to me how easily something good can be destroyed by people who have no idea what they are doing or by cutting corners.

I saw one of those scarf joints in a video recently and wondered what it was for. I didn't know what it was called so I couldn't look it up. I don't mind carving a few of those if that is what's needed. Good to keep in mind.

Doing our best to get a good log builder out here to assess the situation properly. Last year we called every log builder we could find but only one could visit us but he lived on the other side of the country and was just here for a day so couldn't help us. So I have to wrap my head around this myself. Log building is like a dying art, but the more I learn about it the more I realise that traditional building is superior in just about every way except mass profit/production. I'm starting to seethe modern world is geared towards high replaceability where the faster things break down the quicker you repeat purchase. The economy would come grinding to a halt if we built things to last with houses that live for 600 years. Incredible that so many people work for 40 years to pay for a house that is designed to live for only 25.
 
Terry Ruth
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I been reading about wood/logs lately and came across more details on logs yesterday that may help us understand rot better. Always nice to apply and understand with real live samples. Since log walls are orientated with cross grain direction toward liquid phase rain water they are said to be closed to capillary action(defined as transport through the material and/or cracks, crannies) by forces such as pressure, gravity, etc) kinda like a tree sucks water) but still permit some degree of vapor - phase moisture transport to be regarded as "permeable and hygroscopic" materials. So logs do not have a large ability to regulate indoor humidity like clay and lime, or certain chipboard like Durisol. It is best to keep their moisture content dry (below 19%, no more than 29%) Clay can store 50% RH. Along the grain pore size is very large and "capillary open" so water can suck into the material . You can see the vertical logs "checking" (I think that is the proper term) toward the end grain in your pic. The way the checks happen is interesting, wood has tapered tubular shaped cells (kinda like straw), the cell walls fill first then the tube. When drying occurs (usually toward a lower humidity levels outside the log) the outer cell walls starts first but the tube is still full so the outer cell wall expands and cracks since it has no where to dry but outward. Wood is said to be saturated at 28% by weight, dry at 19%....When saturated just like other materials (clay, lime, etc) it drains water if it can. I read some seal up the ends, joints as in your rafter-ridge, rafter-sill with caulk (a natural compatible one, impermeable).

So this may explain rot from the inside too. If someone put a sealer that is vapor impermeable on an already low perm, low capillary, low saturation, log on the cross grain side it could potentially trap moisture in the log by not allowing it to dry. Further, I would think clay plaster over the logs would pull some small amounts of moisture out of them and keep it off the surface for wicking if no one put an impermeable coating on. You definitely do not want a plastic barrier over wood to prevent it from drying.

There are exterior water proofing finishes that produce sufficiently large enough pores for water vapor diffusion, but are too small for capillary uptake....the book just has told me what they are for wood yet (watch my thread). That would allow drying to the exterior and protect it too, unless the outside has high humidity all day and most of the year. If that is the case a high hygroscopic cladding may be best (see my thread for high perm, EMC).

I'm no good with old joinery follow Bill's advice on that, I am learning too. I been around structural loads my whole life. I could make this work with metal, but the chem treats are not natural and eventually wear off. The only other thing I can think of is cut the lower rafters out of the way, spice in an extension to the sill with large diameter as possible steel bolts. 2 at least or 3-4 better. Those rafters look old and weak anyway. Then the steel bolt reacts the bending....If you know how to do static moment analysis, you can proof the proper diameter and pitch of the bolts or not since the old wood may not take it. It is not that difficult, Force = pressure/bearing area of the bolts, knock down the bearing allowable of the wood 50% for a safety/age factor. If this were possible you would not have to take anything but sections of rafter and sill apart to R&R. That looks like a corrugated metal roof with grommet nails in the rafters? It may not be that hard to just take it off, undo the sill and ridge tie like Bill suggest. If it is a large area of sill rot just take all the metal panels off undo all the rafters and replace the entire sill in one piece, rafters as requred....Perhaps seal up all the joints and keep the indoor and addict humidity with ventilation under control.
 
Rob Irish
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That is really interesting.

That sounds about right with the clay. In the room we put clay up on, there was already a really old layer of clay in some sections. This wood around that was dry as a bone, even though it still had an additional plastic/wood based chipboard on it. So the clay definitely helps with that. Meanwhile, there were sections where I would say the last people who renovated and "upgraded" the interior with chipboard. also patched up some places with cement. Comparatively to the clay, these sections were awful.

The roof sheets are asbestos. We don't plan to keep them so we will likely replace them all. I love shingles and also old school straw roofs.

I grabbed a few more photos of the wall plate joints. Actually they all seem to be reinforced or held in by metal hooks of some kind.

Notice there is what seems to me to be an old rafter in the first pic. There are a few of these around and to my knowledge seem to have no purpose. They are just nailed into the batons hanging there - why would they do that? Did they leave the old roof on partially perhaps while they built the new one? I can confirm now for sure that the rafters all do infact extend into the eave. My eyes played tricks on me because on the outside the eave wood is all squared, meanwhile it is rounded inside the roof. I guess they did this for visual reasons.



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Terry Ruth
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It's difficult for me anyway to tell whats going on structurally and why they did things the way they did back then without being there. The depth they halved the top plate to is interesting, almost down to nothing and I see one rafter collapsed from rot down to the next log. As long as that joint is sandwiched between the rafter end and next lower log it does ok if there is no rot. You could splice the way I showed in my pic with bolts that will take lateral loads too, 12" log ties, and you could even add steel straps. If you go wood carving a scarf. I'd never half down to that depth, I'd leave at least 1/2-3/4 or find another way.

The rot does not appear to be from fungi growth to the naked eye anyway, so that leaves fiber saturation and an inability to dry-drain. Across the grain would take water sitting there a while. I don't know if water is accumulating where the rot is but, that would the first place to look. I can't tell without an outside pic but it appears your eve vent is through a corrugation and up to a ridge vent? I see a door at the gable end but no vent? A good rule of thumb is 60-40 split, lower eve vent area 60%, ridge-upper gable 40. That will slightly pressurize the attic so it does not suck conditioned air out of the living space too. Another rule of thumb is 1 Square Foot of ventilation for every 300 Square Foot. It appears the eve vents are a wide open corrugated shape, if the overhangs are not long (2-3 feet better) water could be getting to the plates. Next time it rains and-or high winds go up there and see if water is accumulating and there is good air movement through the upper vents.



Looks like you have your work cut out for you I wish you luck!
 
Rob Irish
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I'm going to just do up a little 3d sketch of your drawing Terry to see if I understand right. Really appreciate all the advice so far.

In the meantime I took a few more photos from the outside if it helps at all.

This is the roof area above the most damaged area. You can see they did some repairs there some time ago so it has been a trouble / leaking spot for a long time. I fixed the leak up last year. It's probably been leaking before that for 10 years. The attic was insulated with a thick layer of sawdust and straw which had started to compost in some spots.



You can see that yellow painted steel plate which is what the metal cable 'tie beam' locks into. There are I think 4 of these.



I don't see the rotten rafter you said. Are you referring to the first pic in my previous post? At the top of that rafter (looks like half a rafter) is a ridge joint as though that used to be the peak of the roof when the house was half as wide. It hasn't broken off.

Is this what you meant by your drawing?




I think you could be right that they didn't get the ventilation right. I haven't been up there in a storm yet but will definitely see if I can figure that out.
 
Bill Bradbury
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Hi Rob,

That sketch looks great, but I would use 2 jacks.

I'm thinking that it may be a better option to build a frame within a frame.

Posts inside the home could support new tie beams that would tie into the existing rafters and then support another set of rafters inside of the originals and tied to the originals in a parallel chord truss style. This would be very strong and allow you to insulate well and reducing the load to the existing shell so it would only need minor repairs.

Or you could use the same method in a queen post truss manner.
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Rob Irish
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I see now Bill.

That is quite simple and doable.

What sort of space between the original and the new rafters? I guess that is where you would insulate.
 
Terry Ruth
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It is not that simple when you are dealing with this old log, now combing new and old, I'll explain more in detail later. Rob I hope you are planning on taking that roof cladding down? I got a feeling it and your open soffits and ventilation are causing a lot of your rot, more later. You do not want to duplicate the current issues.

In the meantime think about where the major load is coming in and what happens when old structure needs to be knocked down to 50% strength due to age and rot when new sub structure is at 100%. Where is the weakest link in the design? AND what effect will the new structure have on the old? How much more life do we expect to get out of the old structure when it is loaded up more at the joints with trusses? Seems to me your old major structure is at the end of it's life cycle due to the environment it has been placed in that needs correcting or it will continue to fail? Estimate all new vs all this new=retro fit, tooling cost, risk, etc, put a price tag on your weakest link failure in the future of combining old/new..The long term math usually leans out to all new, better more sustainable designs known today especially if you plan on keeping it long term.
 
Bill Bradbury
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Well Terry, as a guy who spends all of his time repairing old homes that others wish to replace; I couldn't disagree more!

I have looked at your other post Rob and I think this is very doable as well.

I like to have a roof that has an exterior vent channel and insulation under that, so I would leave at least 2 feet between the two chords. Then you can open up your ceiling and get rid of those ugly cables and rebar.

I would probably use straw/clay as an interior insulative mass wall. This should work well with the exterior logs acting as cladding and mass.



 
Terry Ruth
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Bill, I’m not disagreeing with you other than if you’re going to rebuild that much of the rafter why not just rebuild it all. I suggested that same thing two post ago rebuild the rafter and the tool made it obvious for a truss design. We were trying to not have to a lot of rebuilding, in the OP some have already suggested that, and I personally think this is doable too….just depends on how much cost and labor you want to incur. If I were keeping the place I’d put more money in it so it last another 100 years IF you put to much jacking load on the old structure and it cracks a complete rebuild may be the result anyway.

I’m not sure what the cladding plan is but it appears that cladding is leaking not only from the top but through the soffits. I’d r&R it, that would open up the rafters for a complete rebuild, not partial, makes sense to me anyway. That cladding looking like corrugated tin to me, I don’t see any asphalt shingles. It also appears to be sagging inward in some areas but I can’t tell for sure.

There are a lot of ways to design trusses that have proven themselves, http://www.raftertales.com/home-remodeling/roof-truss/
I am only stating that along with this re-design it is important to understand the rot and correct it. Look at today’s soffit designs, they are closed structure that creates a barrier for water uptake through soffit vents, the baffles assure flow to ridge vents, cans, gable vents……if the venting is wrong the attic will rot.

Lots of attic and soffit vent guild-lines on goggle.

PIC 1 and some of the others indicate a lot of rot and the attic is seeing a lot of moisture, the wood is fiber saturated and is not drying out. Rob, PIC 2 shows the low half depth I was talking about, I find that very thin, but as I said it has lasted up to the rot since it is sandwiched between the rafter and wall in compression. The tie beams take out the lateral loads. I am suggested a splice here in my drawing with these Headloc log ties on both sides of the splice, the head seals water intake. PIC 3 shows the halved or notch completely rotted away as if water is accumulating here. I’m thinking it is getting in from both the cladding and soffit? And it is draining slow causing rot.

I was doing some research on Durisol yesterday since they said they “mineralize” their wood chips. When I goggle mineralized wood petrified wood comes up that seems to last forever. http://creationwiki.org/Petrified_wood

Here are some quotes:

“Wood decomposes extremely fast in environments where trees typically grow. This happens because wood is composed of sugar (cellulose), which is the preferred food for microorganisms such as bacteria and fungi. Even modern pressure-treated woods can not escape decomposition.”

“The speed at which decomposition takes place is determined by the temperature, moisture, availability of oxygen, and the type of wood. Under normal forest growth conditions, most trees decompose completely in only a few decades. Even the species of trees that are slowest to decompose, such as the western red cedar, will disappear completely in under 150 years “

"Uniformitarian geologists frequently tout that fossilization requires millions of years, but there are many modern examples where organisms or artifacts have become fossilized rapidly. Wood can become quickly mineralized if buried or submerged in a highly concentrated salt solution where carbonates are precipitating. There is even a U.S. patent whereby wood can be treated with a silicate solution rendering the characteristics of petrified wood. US Patent for Petrified Wood Patent No. 4,612,050: “A mineralized sodium silicate solution for the application to wood has a composition causing it to penetrate the wood and jell within the wood so as to give the wood the non-burning characteristics of petrified wood.” [2]. Researchers at the Pacific Northwest National Laboratory found a method to create petrified wood in just a few days. "

So perhaps we preserve our wood with a spray application of mineralized sodium silicate? I wonder if that yellow paint is impermeable, I’d sand it off so the wood can breath.

I’m not challenging anyone’s ideas there are MANY ways to skin this cat, obvious is structure like trusses and support wall structure can be added no challenge there anyone can figure out, is the easy part and common. What varies and is inherent to each building is how rot occurs that got my interest in this thread. It appears to me this build may have reached it’s life cycle after 85 years due to the environment, supporting the notion of replacing as much old structure as possible and affordable, especially major load bearing and mitigating future rot.

I find it all interesting. I think there is some good from the past and present, the bad in both cases we can leave in the past.
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Terry Ruth
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Here are the Headloks we are using on our build: Drive them through a few logs should be strong. http://www.homedepot.com/p/FastenMaster-HeadLok-4-1-2-in-Heavy-Duty-Flathead-Fastener-50-Box-FMHLGM412-50/202268258
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Bill Bradbury
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I think most of the repairs could be carried out in situ, resulting in a quick turn-around.

Yes, I think Rob is planning on removing and disposing of the asbestos fiber reinforced roofing. The rafters are in good shape; for the most part it's the log wall that is the issue. By imposting and setting a new tie beam on top of the post and tied to the top plate, you are reinforcing not jacking up the structure.

There will be a significant amount of wood to purchase, but it looks like that is plentiful. Then this allows for insulating and air sealing the structure while venting the roof. I don't have a problem with exposed soffits, but those decisions will be Rob's.

Rob, it seems like you have a good working knowledge of timber framing skills, but you will need to study joints and how to make them. The one I see lacking in your structure so far is a notched lap, it's a lap joint that the male member has a notch in it to prevent pullout. These are pinned as well, but the pin is not what resists pullout, it only holds the halves together. This is what you should be using on the collars and truss chords.

Please ask any questions that arise.
 
Rob Irish
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Terry,

We definitely want to get rid of the cladding on the roof. It is awful stuff that cracks if you put any weight on it. We have the same stuff on a barn roof that extends to the back and I got up and did some repairs last year and made just as many cracks as I fixed just by laying a ladder on it.

That is interesting about fast forwarding petrification Terry. Incredible to think a wood house could last for even longer like that.

It has has been on ongoing debate since we moved here - to start from scratch or fix her up. Most of the advice has leaned on the side of starting again. The thing is however that by fixing this old building, we've learnt so many things about what works and what doesn't, mistakes that I think we would have made if we started fresh.

It is hard still for me to really work out what we're going to do while we still have the indoor ceiling on as we can't fully assess the situation of all the tie beams and wall plates on the inside of the attic until we take out the truck load of saw dust and straw up there. I'm not closed to building new rafters.

I wonder how much the material of the roof effects breathability of a attic as well? Surely a roof that is made of thatch or wood needs less ventilation. This house used to have shingles, and I'd say the roundwood truss was originally made for that.



Bill, I don't think I see any notched laps. Would that mean the previous builder has put all the weight onto the pins? Would you do notch laps on the tie beams as well?

We have all the trees we need here on our property. Many hectares of many years of unmanaged woodlands after clear felling means we have really dense areas of trees all competing just for height so we need to do a lot of thinning.

I'm wondering how to go about building a parallel chord inside the existing truss though. Would you leave the existing collar beams?

Doing a parallel chord would be good in that it gives us an open roof, but also if the roof becomes 2 feet thick, that is less open air to heat up in winter.

We're only just chopping down logs and beams now. Is there a problem with using relatively green logs in a repair job like this? Should I be doing all the sizes about 5% bigger to allow for shrinkage?

 
Bill Bradbury
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Hi Rob,

The notched lap joint is just an improvement over a regular lap, because the pushing/pulling forces on a collar or a truss component can shear the pin. So the notch is added to take those forces off the pin where a mortise and tenon or dovetail style joint is not applicable.

I would probably pull the collars in order to improve them with a notched lap and to notch them to accept the 2 bottom chords to run through to tie into each other with a half lap. The parallel chord truss supports will be notch lapped and pinned, that way you can install them after setting the bottom chords and tie beams.

I am not an expert timber framer, I restore old homes for a living, but I have only built a few things this way. I do however have access to timber frame guru Jay C, White Cloud, since I have been pestering him to teach a timber framed walipini workshop with me in August. I'll ask him and get back to you, since I know that he likes 'em green. I have had troubles with green timber joints opening up, so I don't want to give any advice on that.

In the old days of cedar shingles, no one vented a roof, because the roof is breathable on it's own. I would recommend this if you can do it. Most were without tar paper, so you have to be a really good roofer. I don't think your simple roof will be a problem. The thing about wooden shingles is they swell when they get wet and seal off the air flow until they dry. Then air can exchange freely again.

 
Terry Ruth
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Ironically, I had to go home from an out of state job site to get with our attorney. We were being handed sketches from a non-licensed prime contractor we report to as subs on this job. He can’t draw worth a beans, and he does not understand the difference between load bearing and non and when he needs a PE. The city requires changes like these that differ from the original drawing’s the architect got approved to be resubmitted by the architect for re-approval we said. We stopped work until we get these drawing’s. Made me think of this thread and how some sites are offering health related design solutions (the green non-natural ones) and getting away with it. Rob, I just want to reiterate that my sketches are not being offered to substitute a professional engineer’s stamp of approval as I recommended above, nor my advice on preventing mold related health issues. I have read of the horror stories of businesses dissolving every couple of years to avoid litigation in this book one again I am reading discusses. It is very difficult to design safe structure from limited info off the internet, so take all advice with a word of caution.

Here is what the book has to say about mold, I’ll let you all decide how important ventilation is and stopping water intrusions through soffits, etc….

1. All materials are susceptible (except sheet metal ducts although some claim they have seen it grow). This is one of the conditions, a bio-film food source. Wood it is sugars. Wood also has small traces of formaldehyde averaging 3.7 PPM: http://www.awc.org/pdf/formaldehydefactsheet.pdf
2. Presence of moisture.
3. Low air flow.

The book explains why the first 48 hours to kill the germination stage is critical. The food cannot be realistically eliminated, that leaves keeping materials dry and air flow high. Mold can be hidden in walls, between logs, etc, not seen by the naked eye. Occupants often experience symptoms from these hidden sources prior to visible evidence. Homeowners that assume when everything dries out all is fine are mistaken, dormant spores are still present and cause health hazards. Fungi treatments do not completely remove mold, the material has to be completely removed.
The two main sources are rainwater and indoor condensation. Such damage relates to the homeowner’s inability to control moisture, or a bad building design or build practices that control moisture within susceptible limits.

The book discusses acceptable breathable materials and designs, like wood, that are allowed to breath I discuss on the review thread.
A mix of borate, MGO, and clay makes up a good wood preservative that is fire and rot resistant. I would think the high MGO content in lime type s would work.

From what I read from Jay and others, green lumber has to be aged on site properly and you have to be a master craftsman to deal with it. I’m not so I’ll stick with kiln dried.

Here Jay offers some advice and explanations: http://www.permies.com/t/43286/timber/Timber-Framing-Traditional-Joinery-PICs

According to the link above Western Cedar is the slowest to decompose in its natural environment lasting up to 150 years. I cannot remember but I think the Timber guys I talked to on my job site said it takes longer to dry, and Douglas fur has the highest strength-to-weight ratio. White Oak is rot-resistance.

In my design I’m going with a sealed vaulted ceiling so selecting materials that breathe vapor and xchange air will be important. Not to undermine the importance in vented attics and cladding’s.

Rob Irish wrote:Terry, I wonder how much the material of the roof effects breathability of a attic as well? Surely a roof that is made of thatch or wood needs less ventilation. This house used to have shingles, and I'd say the roundwood truss was originally made for that.


For me, the lesson is if you think you have designed a breathable assemble the need for ventilation can be reduced or eliminated. Your roof cladding is not an example, and who knows what treatments are on your logs? Definitely more of a challenge restoring old perhaps not having all the facts, then new. With that said if it were me as I said I r&r as much as possible, especially given that you have plenty of materials and are doing the labor yourself. Pay a PE to look it over for safety, otherwise the burden of liability for anyone getting hurt now or in the future is on the designer, you, for errors and omissions. We explained by not accepting anymore of his sketches we are not only protecting ourselves but him and the owner.

BTW: I have been designing structures for over 30 years, CAD_CAM from day one. AutoCAD back in the day, CATIA today, I remember when the solid body was created, it really helped identify interference's in design by "clash" auto-checks. In CATIA manufacturing there are no 2D prints anymore, all is built off the 3D solid you show in your renders. I don’t see the construction industry going paperless anytime soon.
 
Rob Irish
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Thanks for all that information Terry and Bill. So much to take in and really think about.


 
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